Abstract : The communications subsystem bandwidth measurement shows that the CSMA/CD network operates about 12 times as fast as the serial link network. The EPL process bandwidth measurement shows that there is at best a twofold decrease in completion time by using the CSMA/CD channel. This indicates (in the XDCS system) that the communications software has more impact on performance than does the bandwidth of the underlying network. The network overhead benchmark shows that when the percentage of time computing in EPL is greater than 70 percent of the total completion time, the communications delays imposed by the network are more than offset by using two processing elements. When the time in EPL is less than 70 percent of the total completion time, it is better to perform the computation on one cpu. This crossover point is not dramatically changed by the system used to perform the measurement.